Two Pakistani security guards protecting health workers in an anti-polio drive in the country's north-west have been killed in a bomb attack.
It was the latest incident against the government- and UN-backed effort to eradicate the disease.
The bomb killed a police officer and a member of a volunteer peace committee in the village of Malikhel outside the provincial capital of Peshawar. The victims were with workers administering anti-polio vaccine to local residents.
In 2011 Pakistan had 198 confirmed polio cases, the highest in the world. It was able to bring that down to 58 in 2012 through an aggressive vaccination program. But the success has come at a cost.
Militants who oppose the vaccinations often target workers delivering the vaccine and threaten people who want to get their childrenvaccinated.
Two powerful Pakistani Taliban militants have banned the programme from two tribal regions in the country's north-west, North and South Waziristan, over the past year because of their opposition to US drone strikes.
They claim the vaccine is meant to sterilise Muslim children and accuse health workers of being spies. The allegation gained ground after the CIA used a Pakistani doctor to try to confirm the presence of Osama bin Laden in 2011 under the guise of an immunisation program.
Many suspect the Taliban of carrying out the murders, although the group has denied it.